Prep: Preheat oven to 350°F. Line a light-colored metal/aluminum 9×13-inch pan with parchment, leaving an overhang for easy removal.
Whisk butter, sugar, and cocoa: In a large bowl, whisk together melted butter, sugar, and cocoa powder until smooth and glossy, ~2 minutes. (You want to whisk it really well to help create that shiny top). Start Timer
1 cup unsalted butter, 2¼ cups granulated sugar, 2/3 cup Dutch-process cocoa powder
Add the rest of the wet ingredients: Whisk in eggs, egg yolk, vanilla, and salt until fully combined.
3 large eggs + 1 egg yolk, 2 tsp vanilla extract, 1 tsp fine salt
Add flour: Fold in flour until just combined.
1¼ cups all-purpose flour
Fold in chocolate chips: Stir in mini chocolate chips.
1 cup mini chocolate chips
Pour into pan: Spread batter evenly in the pan.
Bake: Bake for ~24-28 minutes, until the edges are set and the center is just set. Careful not to overbake. Slightly underbaked will give you a fudgier brownie fry! Start Timer
Cool + chill (important!): Let brownies cool completely in the pan. Then refrigerate for at least 2 hours (or freeze for 30-45 minutes) until firm. This step is key for clean “fry” cuts. Start Timer
Cut into fries: Lift brownies out using parchment and place on a cutting board. Using a wavy french fry cutting tool to cut into even fry shapes about 3/4 inch wide and 3-4 inches long. Serving options: Garnish with flaky sea salt or a dusting of powdered sugar if desired and dunk the brownie fries in melted chocolate, chocolate ganache, caramel sauce, or just a cold glass of milk. Great for parties and kids!